Question
A 25-year-old woman comes to the physician because of pain and weakness in her left leg that started 2 days ago while running a marathon. Physical examination shows impaired flexion of the left knee joint and impaired extension of the left hip joint. An MRI of the left lower extremity shows injury to the long head of the biceps femoris muscle and the semitendinosus muscle. Which of the following is the most likely origin of the injured muscles?
| A. |
Superior pubic ramus
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| B. |
Ischial tuberosity
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| C. |
Anterior superior iliac spine
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| D. |
Greater trochanter
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Show Answer
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Correct Answer � B
Explanation
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Ischial tuberosity
- The long head of the biceps femoris and the semitendinosus muscle originates from the ischial tuberosity.
- The muscle belly of the long head of the biceps femoris joins together with the short head of the biceps femoris to form a conjoined tendon, which inserts primarily into the lateral aspect of the fibular head.
Superior pubic ramus
- The superior pubic ramus is part of the pubis and forms the anterior part of the acetabulum. It is the origin of the adductor longus muscle, which runs along the inner side of the thigh, inserting on the linea aspera.
- The long head of the biceps femoris and the semitendinosus muscle do not originate from the superior pubic ramus. Also, the adductor longus muscle performs hip adduction and flexion, but not knee flexion or hip extension.
Anterior superior iliac spine
- The anterior superior iliac spine is an anatomic landmark on the ilium, which forms the lateral part of the pelvic girdle.
- It is the origin of the sartorius muscle, which runs along the inner side of the thigh and inserts on the medial upper side of the tibia.
- Although the sartorius facilitates knee flexion, it does not allow for hip extension. Instead, it performs hip flexion.
- The long head of the biceps femoris and the semitendinosus muscle do not originate from the anterior superior iliac spine.
Greater trochanter
- The greater trochanter lies on the lateral aspect of the junction between the neck and shaft of the femur.
- It is the origin of the vastus lateralis muscle, which is one of the four heads of the quadriceps femoris muscle, but it is not the origin of the long head of the biceps femoris or the semitendinosus muscle. Also, the vastus lateralis performs knee extension but not knee flexion or hip extension.
